India's attempts to stop England wresting their No1 Test ranking ran into immediate problems on the opening day of the series when Zaheer Khan, the most experienced member of their pace attack, fell prey to the sort of injury that has dogged his entire career.

Zaheer limped off with a strained right hamstring midway through a rain-hit first day here to leave India once again fearing the worst and cagily refusing to reveal details about whether, as seemed inevitable, a scan would be necessary.

With four Tests scheduled in a five-week period, and Zaheer's lack of durability well known, not just this Test but the entire series could rest on the result of overnight medical assessments.

Zaheer had justified his sixth place in the International Cricket Council's Test bowling rankings, swinging the ball under overcast skies. His duel with Andrew Strauss has been identified as a pivotal battle of the series – and he claimed first blood, dismissing Strauss with a bouncer as the England captain's run of failures against left-arm fast bowlers persisted.

But Zaheer's next applause was tinged with sympathy as he left the field prematurely, 42 overs into the first day, with figures of two for 18 in 13.3 overs. England's task immediately looked more straightforward and Jonathan Trott and Kevin Pietersen guided them to 127 for two before rain and bad light caused an early conclusion.

Duncan Fletcher, coaching India for the first time against England, where his reputation was chiefly made, did not disguise the damage that Zaheer's absence could cause. "It was quite a loss for us at that stage," he said. "He is the bowler we miss the most. Probably the other bowlers lack his experience. Zaheer bowled very well and him going off was a big miss. He was the one who could have got us that third wicket. Then we would have ended up having a very good day."

India will fear a repeat of the sort of ill luck that Zaheer has suffered throughout his career, notably on tours of Australia. In 2003 he limped out of the first Test, missed the second one and managed to bowl in only one innings in the third. Four years on he fared little better, playing only in the first Test in Melbourne before missing the rest of the series.

Fletcher refused to speculate how much India's challenge would be weakened if Zaheer's involvement in a series is cruelly curtailed once more. "I don't think you can look that far down the line," he said. "You could turn round and say: 'What happens if Tendulkar gets injured tomorrow, what impact will it have?' So let's wait until tomorrow and we will have a better idea of how we will progress."

Instead of hailing what might have been an excellent day for India, Fletcher was left to rue his pace bowlers' difficulty in coming to terms with the demands of the Lord's slope on a swing bowler's day. "We would have been very happy with three wickets," he said. "To come from Somerset, where it didn't swing, it was a bit difficult to readjust. We could have bowled slightly fuller lengths and with it swinging around a bit it was difficult for our bowlers to get used to that and get their lines right.

"When I was with England there were players who used to bowl at Lord's quite often and the slope still could affect their bowling if they had a break from it."

Trott also benefited from India's close-catching limitations as two edges evaded Rahul Dravid at first slip. "Jonathan Trott is a high quality batsman and he is the gentleman who got away with two chances today," Fletcher said. "He shows a calmness at the wicket and his statistics show he is a very good player. They were two very difficult chances. We have seen that happen at Lord's on numerous occasions."

Trott, meanwhile, insisted he would not be getting carried away by the prospect of facing a diminished India attack. "As for Zaheer Khan, I expect the guy to be ready and bowling tomorrow; that's the way we prepare," he said.

"If he's injured so be it, we will readjust and focus on whoever has the ball in their hand and is bowling at us."